1. Field of the Invention
The invention relates generally to the field of threaded fasteners. More particularly, the invention relates to a threaded insert for repairing threads in a bore. More particularly yet, the invention relates to a tool for installing a threaded insert with locking keys into a tapped bore.
2. Description of the Prior Art
Threaded inserts are commonly used to repair or strengthen tapped bores. For example, it is sometimes necessary to repair threads in a bore because the threads have become stripped or otherwise damaged. Thread repair generally comprises the steps of drilling out the damaged threads, tapping the bore to a larger diameter, and threading a threaded insert into the bore to provide an internal threaded diameter that will receive and securely hold the threaded fastener. Often, a threaded insert is used to strengthen a bore made of material that is otherwise too soft to securely hold a threaded fastener, particularly one that is repeatedly inserted and removed. In this case, a threaded insert of hardened material is inserted into a tapped bore of softer material to provide a rugged and durable threaded bore.
In order to install a threaded insert, the insert is properly aligned with the longitudinal axis of the tapped bore, screwed into the bore, and secured. One conventional method of securing the insert in the bore is to provide the threaded insert with locking keys. The conventional insert generally has two or four locking keys that extend upward from keyways that are evenly spaced around the outer perimeter of the insert. After the threaded insert has been threaded into the bore, the locking keys are driven down into keyways, forcing the keys to bite into material in the insert and in the bore, thereby securing the insert against radial movement. One common difficulty with installing the threaded insert is that the locking keys are relatively slender and are in danger of being bent, splayed, or damaged when the insert is screwed into the tapped bore.
Conventional tools for inserting threaded inserts generally comprise several components that move relative to one another and cooperate together to perform the various operations required to properly install the insert. Such a tool is disclosed by Schron et al. (U.S. Pat. No. 5,617,623; 1997). The tool has a drive means, a body, and a press. The body of the tool has a first end with an external threaded shaft onto which the drive means is threaded and a second end with an external threaded shaft onto which the press is threaded. A sleeve encircles the press and is movable relative to the press. A thrust bearing is assembled on the body above the press. The external threads on the threaded shaft on the second end mate with the internal threads on the repair insert, which is rotated down into the tapped bore until the locking keys on the insert hit against the impact face of the press. The drive means is a handle that is used to rotate the body to thread the insert into the tapped bore. The sleeve is moved longitudinally down toward the insert over the locking keys. The socket of a power tool is then placed on the drive means and a rotational force applied to the drive means, which drives the body, the press, and the insert rotationally, threading the insert into the tapped bore and then forcing the locking keys down into the keyways along the outer side of the insert.
The fact that the threaded insert tool of the type disclosed by Schron et al. is constructed of individual parts, some of which move relative to each other in the process of executing the task of inserting a threaded insert, is a disadvantage. The individual parts must be machined with a relatively high degree of precision to ensure that they will function properly together and they must be assembled. The required manufacturing and assembly processes increase the cost of producing such a tool. A tool that comprises multiple moving or cooperating parts also inherently provides sources of tool failure, the failures arising from worn parts that no longer function properly or contamination between parts that prevents them from moving or cooperating properly. As is generally known, threaded inserts are often used in an environment that is laden with contaminants, such as in a machine shop or a car repair shop, and care must be taken to keep the insert repair tool free of dirt and other contaminants.
A single-body insert tool, such as the tool distributed by the Christopher Company for installing ROCK SOLID INSERTS, eliminates some of the disadvantages of other conventional tools, in that it has no moving or cooperating parts. The tool is a cylindrical body with a strike end and an insertion end. A pilot extends from the insertion end for guiding the tool onto the threaded insert. Keyways are provided around the outer perimeter of the insertion end for receiving the locking keys of the threaded insert. A continuous circular groove, concentric to the pilot, is machined into the face of the insertion end. The threaded insert is placed over the pilot such that the locking keys of the threaded insert are secured in the tool keyways. The insert is screwed into the tapped bore, the insert tool lifted slightly and rotated about its longitudinal axis so that the upper ends of the locking keys slide into the groove. An impact force is applied to the strike end of the tool to drive the locking keys into the keyways provided on the threaded insert. Once the tool has been forced down onto the threaded insert as far as it can go, the tool is lifted from the insert. At this point, the upper ends of the locking keys protrude upward beyond the upper edge of the threaded insert. In order to drive the locking keys flush with the upper edge of the insert, the endface of the pilot is placed on a locking key and an impact force applied to the strike end of the tool. Typically, a threaded insert has four locking keys, and the step of driving the locking key flush with the upper edge of the insert is repeated for each locking key.
The disadvantage of the conventional single-body tool is that each locking key must be driven down into the tapped bore individually. This requires repetitive installation steps and also increases the risk that the person installing the insert will accidentally pinch or injure himself during the installation. A further disadvantage of this tool is that it does not correct for a misalignment of the locking key. A misaligned key makes it very difficult, if not impossible, to drive the key properly into the keyway on the insert in the tapped bore.
What is needed, therefore, is a threaded insert tool that provides a means of inserting a threaded insert with locking keys into a tapped bore while simultaneously protecting the locking keys. What is further needed is such a device that corrects a misalignment of the locking keys. What is yet further needed is such a device that simultaneously drives all the locking keys completely into the threaded insert.
It is an object of the present invention to provide a threaded insert tool that properly aligns and inserts a threaded insert into a tapped bore, while simultaneously protecting the locking keys from damage. It is further an object to provide such a tool that corrects a misalignment of the locking keys. It is a yet further object to provide such a tool simultaneously drives all the locking keys completely into the threaded insert so that the upper ends of the keys are flush with the upper edge of the insert.
The objects are achieved by providing a single-component threaded insert tool. The threaded insert tool according to the invention comprises a body with an insertion end for threading the insert into a threaded bore and a strike end for receiving impact blows. The insertion end of the tool has an insertion face, tool keyways evenly spaced around the outer perimeter of the insertion end. A cylindrical pilot or guide extends from the insertion end, coaxial to the longitudinal axis of the tool, and guides the tool into the insert. Key-retaining means are provided on the insertion face. The tool keyways are adapted to receive and engage the locking keys of the insert when the insert is slipped over the pilot in preparation for installation. The key-retaining means may be an individual bore provided for each locking key or a partial circular groove that opens from each tool keyway. The key-retaining means according to the invention may also include an alignment means to re-align misaligned locking keys. In this case, the key-retaining means is provided with a contoured inner surface that urges the locking key into proper alignment when the insert tool is forced down against the locking keys during installation of the insert. A timing mark may be provided on the outer perimeter of the insert tool to aid in ensuring that a flat strike surface is provided above each of the locking keys for driving them simultaneously down into the insert. It is noted that the threaded insert tool according to the invention is dimensioned to receive and install a threaded insert of a particular size that has two or four locking keys. Thus, the outer diameter of the pilot corresponds to the inner thread diameter of the threaded insert, and the length of the pilot corresponds approximately to the length of the insert, and the outer diameter of the insertion face corresponds to the diameter of the upper face of the outer thread on the threaded insert.
Installation of a threaded insert using the threaded insert tool according to the invention is as follows: The threaded insert is placed on the pilot and moved toward the body of the tool so that the locking keys are received into the corresponding tool keyways. The threaded insert is then placed in the tapped bore and the tool rotated to screw the insert down into the tapped bore. The tool may be rotated manually or with a power tool.
Once the insert is threaded into the bore to the desired depth, the tool is lifted up from the insert until the locking keys are free of the tool keyways. The tool is then rotated slightly and lowered over the insert such that the upper end of each key is received into the corresponding key-retaining means. An impact force is applied to the strike end of the tool that is sufficient to drive the keys down along the sides of the threaded insert in the tapped bore. A hammer or other suitable tool is used to apply the impact force to the strike end. Once the face of the insertion end of the tool is flush with the upper surface of the threaded insert, the tool is lifted off the keys and rotated until the timing mark aligns with one of the keys. The insertion face now provides a flat strike surface above each of the locking keys. An impact force is again applied to the strike end of the tool with sufficient force to simultaneously drive the keys down into the bore until the upper ends of the keys are flush with the upper edge of the insert.
The device according to the invention is suitable for manual and automated insertion of threaded inserts. The body of the tool may be contoured to enable location of the tool within a jig in an automated manufacturing or assembly process. As mentioned above, a hammer or other suitable tool is used to strike the tool and thereby drive the keys down into the bore.